Steroid sulphotransferase and 17 beta-hydroxysteroid dehydrogenase activities in Ishikawa human endometrial adenocarcinoma cells

The present studies concern sulphotransferase activities for estrogens and other steroids, and 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activities for estrogens in Ishikawa endometrial adenocarcinoma cells. When physiological concentrations of various estrogens (estrone, estradiol, estriol) are incubated, most of the transformation product is the respective sulphate. The sulphotransferase activity is very rapid, and 2 h after incubation 70-95% are converted to the sulphated form. Sulphates are found exclusively in the culture medium, which suggests that as soon as the sulphate is biosynthesized it is secreted to the medium. Comparative data using neutral steroids (dehydroepiandrosterone, testosterone, and pregnenolone) show that sulphotransferase activity for these compounds is very limited. In another series of studies, 17 beta-HSD activity was explored for the interconversion estrone <-> estradiol. At low concentrations (5 x 10(-9)-5 x 10(-8) M), when estradiol (E-2) is incubated, most of the unconjugated material remains as E-2 in the cellular compartment, but at high concentrations (5 x 10(-7)-5 x 10(-6) M) a great proportion (70-80%) of the E-2 is converted to estrone (E-1). On the other hand, after incubation of E-1 at all concentrations most remained as unchanged E-1. It is suggested that, in Ishikawa cells, at very low concentrations of E-1 or E-2, sulphotransferases are predominant, but when this enzyme is saturated 17 beta-HSD activity is orientated to the oxidative form. (C) 1997 Elsevier Science Ltd.